Bone Health and Bone-Targeted Therapies for Prostate Cancer Guideline Endorsement

An interview with Dr. Philip Saylor from Massachusetts General Hospital on "Bone Health and Bone-Targeted Therapies for Prostate Cancer: ASCO Endorsement of a Cancer Care Ontario Guideline." This guideline includes recommendations for management of osteoporotic fracture risk in nonmetastatic disease and interventions for men with castration-resistant prostate cancer metastatic to bone. Read the full guideline at www.asco.org/genitourinary-cancer-guidelines.

Transcript

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The purpose of this podcast is to educate and to inform. This is not a substitute for professional medical care and is not intended for use in the diagnosis or treatment of individual conditions. Guests on this podcast express their own opinions, experience, and conclusions. The mention of any product, service, organization, activity, or therapy should not be construed as an ASCO endorsement.

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Hello, and welcome to the ASCO Guidelines Podcast series brought to you by the ASCO Podcast Network, a collection of nine programs covering a range of educational and scientific content and offering enriching insight into the world of cancer care. You can find all the shows, including this one, at podcast.ASCO.org.

My name is Brittany Harvey, and today I'm interviewing Dr. Philip Saylor from Massachusetts General Hospital, lead author on "Bone Health and Bone-Targeted Therapies for Prostate Cancer: ASCO Endorsement of a Cancer Care Ontario Guideline." Thank you for being here today, Dr. Saylor.

Oh, it's my pleasure.

First, can you give us a general overview of what this guideline covers and about the endorsement process?

Yes. So the Cancer Care Ontario has a program in evidence-based medicine, and they periodically put out clinical practice guidelines for management of a whole variety of topics. And they relatively recently put out a publication on bone health and bone-targeted therapies in prostate cancer.

And so that's a really big topic because bone health is such a big part of prostate cancer care across the entire range of scenarios that patients can face. And their guideline addresses topics all the way from osteoporosis and fragility fractures and that risk as it relates to GnRH agonist, androgen deprivation therapy that men can get for really any prostate cancer scenario, goes all the way from that to improving quality of life in patients who have bone metastases that have progressed despite systemic therapy. So it's really a very broad series of topics that they addressed.

And so when they put out that guideline, ASCO identifies it as something that's very relevant to the ASCO community and goes through, then, a formal process of reviewing the methodology of those guidelines and then having an expert panel discuss the quality and evidence of the guidelines and really provide, if appropriate, an endorsement and some additional discussion of those topics.

So what are the key recommendations of this guideline?

They really have four sort of subtopics within this bone-themed guideline that are addressed and discussed in a fair amount of detail. And each one of those four topics deserves some of its own discussion. The first topic is osteoporosis and risk for just fragility fractures, like hip fracture and vertebral body compression fractures. That's one.

The second is potential prevention of bone metastases in a patient that does not yet have bone metastases. The third one is management of castration-resistant prostate cancer metastatic to bone. And the fourth one is symptomatic management of men with CRPC metastatic to bone. So it is probably worth discussing each one of those, in some detail, one by one.

So for the osteoporosis fracture risk question, Cancer Care Ontario, their recommendation really is that men with non-metastatic prostate cancer at high risk for fracture who are receiving ADT should be considered for the osteoporosis dosing of denosumab. And in situations or places where denosumab is not available, then patients can consider a bisphosphonate as an alternative.

So we had a fair amount of discussion of that recommendation. We endorsed that recommendation. And I guess my personal emphasis would be that osteoporotic fracture risk is really the biggest challenge to that is not forgetting about it.

So you can often have men who are in a good prostate cancer scenario, likely to be cured by their therapy. They're going to get some duration of ADT. And they look healthy as they sit there in clinic with you. They're likely to do well from a prostate cancer standpoint.

And it just would be so easy not to adequately screen for osteoporotic fracture risk, and just not to remember that because so many of our discussions together in clinic are focused on the prostate cancer more than the broader health questions. And so, I mean, to me, I think not forgetting about this issue is really one of the most important things to emphasize in any discussion of osteoporosis.

And so really, it's a fairly simple problem to screen for and manage. Most men should be, if they're going to be on any duration of ADT, should be tested with a bone density test, a DEXA scan. It's really a fairly inexpensive and easy test for getting a sense for where their bone health is as they begin.

And I usually tell my patients in clinic that most men don't need any new prescription medicines to manage that risk, but we'll never figure out the ones who need it unless we go through the very disciplined systematic work of doing that screening. And then among those who really do deserve treatment, it's really denosumab at the osteoporosis dosing or a bisphosphonate. Really, any of those choices really works well for improving bone mineral density.

One of the big ASCO discussion points is that denosumab is the only medicine that's been shown definitively to improve fracture risk in this setting. But that's really a product of denosumab being studied in a really large prospective randomized controlled trial. And so that's one where they required more than 1,000 patients in order to assess that fracture endpoint.

So the reason, perhaps-- probably the most important reason that bisphosphonates have not been shown to improve fractures is that none of them have been studied in such a big study. The bone mineral density trials that have studied bisphosphonates are all on the order of maybe 30 to 100 patients rather than 1,000. So really, in many clinical settings, cost and convenience are important considerations. And when those are factored in, it's often very reasonable to use a bisphosphonate rather than denosumab, though either one really could be considered a gold standard. So that's point number one from the guidelines.

Number two really discusses the issue of prevention of bone metastases. And so there are a couple of sub-recommendations from Cancer Care Ontario. But really, the most important point from that is that there is no bone-targeted drug that has been shown to prevent or delay the development of the first bone metastasis. So a number of different studies have tried to address this question in slightly different clinical scenarios.

But the bottom line is, we don't use bone-targeted medicines to prevent the first bone metastasis. And so there's always been sort of an attractive potential effectiveness there because you think if your bone-targeted therapy changes the bone microenvironment, could the natural history of prostate cancer play out differently? But the answer is that we really don't have any convincing evidence of effectiveness on that front using any drug, in any situation. So that's a pretty easy one to summarize.

For the third category of situation that's addressed in the guideline really relates to castration-resistant prostate cancer metastatic to bone. And so there are three sub-recommendations there. In that situation, either zoledronic acid or denosumab in monthly dosing at the skeletal event preventing dosing is a gold standard and reasonable to pursue. So that's one thing.

In men with symptomatic disease, radium-223 can be considered, both to prevent skeletal events and to improve health-related quality of life. And then, finally, all radiopharmaceuticals can be considered in that situation for palliation of bone pain. And so we endorsed those recommendations as well.

And we added a fair amount of discussion about how to optimally support men's health in those situations. For one thing, it's important to note that monthly zoledronic acid or monthly denosumab, whichever is pursued, is a fairly intensive osteoclast-targeted therapy. And so the studies that formally establish those as gold standards in that setting, they really only treated for about two years, plus or minus. So we don't know a lot about the safety of that intensity of therapy beyond two years.

And so that's an important consideration, because there are many men who do well, thankfully, for a lot longer than two years in the castration-resistant setting with bone metastases. And so we really do, as clinicians, need to respect the possibility of toxicities, especially osteonecrosis of the jaw seems to be a much, much more common phenomenon with longer durations of treatment and with these more intensive regimens. So that's one thing that deserves a lot of attention by clinicians.

The other thing is that dental evaluation and proactive dental care before and during any of these bone-targeted therapies is really an important issue not to miss. So the highest risk for having osteonecrosis of the jaw is in patients who are on one of these intensive regimens and then need to have invasive dental work when they're already been started on one of those regimens. Those are the jaws and mandibles that seem not to heal as well.

And so ideally, every patient that is going to go on intensive osteoclast-targeted therapy really should be evaluated by a dentist with the question of whether there's any dental work that really needs to be done proactively before the start of one of those medicines. And so I always say I have to be humble as a medical oncologist to say I really know little to nothing about teeth. And so I have to reach out to my colleagues in the dental field to tell me which are the patients that need to do something ahead of time and heal before they start one of these medicines. So those are a couple of important points.

And then the other thing that's really not a new piece of information but is important to emphasize is that it's really monthly therapy with denosumab or zoledronic acid should really be used only for patients with castration-resistant prostate cancer metastatic to bone. So the patients who are responding to their systemic therapy really seem not to benefit from the bone-targeted therapy. And that's likely because any systemic therapy that's controlling the prostate cancer, in general, that's active against the cancer, in general, is going to prevent skeletal complications. We just have a lot fewer of those events, thankfully, when the disease is under control.

And then, finally, the fourth category of recommendation addresses symptomatic castration-resistant prostate cancer metastatic to bone. And that's a situation where the radium-223 given in the typical once per month times six series of treatments is a gold standard, improves health-related quality of life and overall survival.

I think one of the important discussion points on that front relates to recent clinical trial data that examines the use of other secondary systemic therapies in addition to the radium. So we have a prospective randomized study that looked at abiraterone with or without radium. And what it really showed was that the combination of abiraterone and prednisone with radium resulted at a very high rate of fractures and worsened overall survival. So that's really a combination that should absolutely not be pursued outside of a clinical trial.

And so that's an important thing to know, but it's also sort of a cautionary tale that if we're tempted to combine other secondary medicines with our radium treatment, we really don't have a lot of evidence for the safety or efficacy of doing that. So that's the sort of thing that really should be reserved for clinical trials. And those are probably the most important-- those are the four main topics addressed by the guidelines. As you can tell, it really includes situations that are relevant to just about every man who receives systemic therapy for prostate cancer.

Absolutely. And thank you for that comprehensive overview and those considerations of the guideline endorsement panel. Why if this guideline important? And how will it impact practice?

So I think there's really sort of two main ways that it's important to the reader in 2020. I'd say, first of all, as a reminder and sort of educational promotion of awareness of the things that we already know but are easy to overlook. And I think the things that are really there are that it is easy to focus on the cancer therapy and easy to overlook the bone-targeted therapy.

So as we have an increasing number of systemic therapies that are active against the cancer itself, and as we have sort of, in the best possible way, more options and more molecular considerations for our prostate cancer patients, we really can't forget to do the fundamentals, like doing monthly zoledronic acid or monthly denosumab in men with castration-resistant disease that's metastatic to bone. So I think that's the kind of thing that would be easy to forget, but that we shouldn't.

And the second subtopic there would be screening for osteoporosis in any man who receives ADT. And again, that's something that-- osteoporosis or someone at high risk for fragility fracture, that's an asymptomatic situation until the fracture occurs. And then at that moment, you're really thinking back and saying, man, I wish I'd done something three years ago, or five years ago, or 10 years ago to improve bone health so that this wouldn't have happened in the first place.

So it really is up to us as the clinicians caring for these prostate cancer patients to advocate for their general health in a way that includes their bone health. We just have to really not forget to screen for osteoporotic fracture risk. So I think those reminders of things that we already know but are really easy to miss, I think that's one aspect of this.

And I think the other is just discussion of the data. It really adds some richness to the topics. And we do have these updates in an emerging field, particularly when it relates to radium-223. It seems like a drug really on, like, a drug strategy that could easily be paired with other drug strategies because it's reasonably well-tolerated.

But we learned, really especially from that clinical trial experience of radium with abiraterone, we really learned that freewheeling combinations are not necessarily safe and not necessarily effective. And so we have to just be mindful of recently emerging data and have an ear to the ground about ongoing clinical trials, sort of how to best combine and sequence all the different medicines that are sort of in our back pocket.

And finally, how will these guideline recommendations affect patients?

Yeah. I mean, I think bone health is really just so important to every patient with prostate cancer. And it's almost, for clinicians, it's almost an educational issue where we have to help our patients understand how important bone health is. When we talk in clinic about a DEXA scan to look at bone density, a lot of men really look at me a little bit blankly. They think of osteoporosis more as this sort of issue that women deal with more so than men.

But I always talk about, if you imagine having a hip fracture and needing hip surgery, or if you think about the pain and the postural changes that happen with vertebral body compression fractures, we really have to do something before any of those things occur. And most men agree with me if you put it in those practical terms. It's just the kind of thing that you have to take a couple of minutes out of your clinic visit to make sure that you address.

And the other thing really is, in men who have more challenging prostate cancer metastatic to bone, even life-threatening prostate cancer, all the complications that can happen later in the course of disease, we really need to do the best possible job not only to keep men living longer, but also to make sure their quality of life is the best it can possibly be.

And that's really-- and most of the time when prostate cancer starts to become a physical burden as it progresses, it's really a physical burden that's centered on bones and skeletal health. And that can have an effect on comfort. That can have an effect on mobility. And these things are hugely central to quality of life. So the impact on patients, all the way from osteoporosis to bone metastases, really, it's just such a central theme within the management of everybody who has to face prostate cancer.

Thank you for your work on this important guideline, and thank you for your time today Dr. Saylor.

Oh, it's my pleasure. We got to keep working to get the word out there and have the optimal management for all of our patients.

And thank you to all of our listeners for tuning into the ASCO Guidelines Podcast Series. To read the full guideline, go to www.ASCO.org/genitourinary-cancer-guidelines. You can also find many of our guidelines and interactive resources in the free ASCO guidelines app available in iTunes or the Google Play Store. If you have enjoyed what you've heard today, please rate and review the podcast and be sure to subscribe so you never miss an episode.

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